This invention generally relates to the field of rotary driven cylindrical cutter devices and scarifiers for use in roadway surface milling. More particularly, the present invention is directed to tooth and retainer inserts for such rotary driven cylindrical cutter devices and scarifiers that can be used on equipment for modifying the surface of an existing road, and in particular, to equipment for smoothing areas of existing pavement by removing bumps, upward projections, and other surface irregularities, removing paint stripes, and milling shallow recessed to receive roadway edging and marking tape.
In general, roadway surface milling, planing, or reclaiming equipment disclosed in the prior art includes a rotary driven cylindrical comminuting drum which acts to scarify and to mine the top portion of the asphaltic road surface in situ. Road planning machines are used to remove bumps and other irregularities on the surface of a road, runway, taxiway, or other stretch of pavement. This planning effect is typically achieved by grinding the paved surface so that the grinding depth may vary slightly, but the surface produced by the grinding unit is more level than the original surface. The road planning machine typically includes a grinding unit that is powered by an engine or motor. A tractor is attached to, or integral with, the grinding unit for propelling the grinding unit against the paved surface in a desired direction.
In some prior art devices of this type, a plurality of cutter bit support members are connected by bolts or by a weld to the curved surface of a drum or to flighting fixed to a drum surface. The plurality of the support members can be arranged end-to-end so as to form a more or less continuous helical pattern. The top surface of the helically arranged support members may be elevated above the curved surface of the drum. The top surfaces of the cutter bit support members can include angled openings into which conventional cutter bits are received. The cutter bits can be a conical cutter with preferably a tungsten carbide tip or the like. The tip can have a variety of shapes.
One example of a cutter bit holder and drum is disclosed in U.S. Pat. No. 5,884,979 to Latham. Here, the drum surface omits any flighting, but includes a plurality of spaced recesses arranged in a preselected pattern, each recess being defined by a generally circular upper edge and including a bottom surface depressed below the driven member rotatable surface. Each cutting bit holding element has a body portion having at least one aperture receiving the cutting bit and a lower portion having a generally cylindrical outer surface sized to be received in only one of said recesses. The lower portion has a reference lower end abutting the recess bottom surface with a locating element engaging the cutting bit holder element lower end with a niche within said recess for orienting the cutting bit holder with respect to said cutting direction. When the cutting bit holding elements are situated within the recesses, they are secured in position by means of a weld line joining the cutting bit holding element to the surface of the drum in a line outside of the upper edge of each recess. In the event of wear or catastrophic failure of one or more of the cutting bit holding elements, the worn or failed element must be removed from the assembly. Replacement of the holding element requires the use of a cutting torch, and the welding of a new support member in place. This is a time-consuming repair job which results in considerable expense to a mining machine operation, and results in a decreased rate in mining.
Despite the availability of such devices, there exists a need in the art for an apparatus having a cutter bit insert for a milling drum, preferably without flighting, that is capable of removable attachment to the drum, yet is resistant to loosening upon rotation of the milling drum. There is also a need for a cutter bit a cutter bit having low profile above the drum so that the total diameter of the drum including cutter bits is less than about 18 inches. There is also a need for a cutter bit that can be quickly removed from the drum and replaced so that the down time experience during cutter bit replacement is minimized.